2000, Order accepted by GM 4-16-09
3000, Order accepted by production control 4-16-09
3300, Order scheduled for production 5-21-09
3800, Order produced 6-12-09
5000, Delivered to the dealer 6-25-09
6000, Delivered to the customer 6-27-092SS Black/Black-RS-Auto-Sunroof

Yea guy's, I work at a dealership and can personally tell you that once you're passed 3000 you can make changes, but it will push your target production date back. I just went through the whole process with a ZR1. The car is being built in black and has been accepted into "3000" status already so it will be built the week of July 27th. To change the color to yellow I had to call GM and they told me I could do it, but they would take the order out of "3000" status and put it back into the beginning order status where I can go back in and select the color (yellow). By doing this I push back my car by almost two months. I said forget it and left it black. So you can do it, just be prepared to wait a little longer.